1. Field of the Invention
The present invention relates to an axial-flow fan and, more particularly, to an axial-flow fan that connects a plurality of rotor vanes in series in a single fan.
2. Description of the Related Art
The axial-flow fan is a popular fan device that has the features such as a simple structure, low cost, and a high air flow rate. These features have made it widely used in various systems as an air conditioning or ventilating device, for example, as the ventilation fan in a computer system.
In general, since the total pressure of the axial-flow fan is lower, the axial-flow fan cannot fully develop a high flow rate in a system of a high resistance. Therefore, in the case that a high total pressure is needed, two or more axial-flow fans are conventionally employed in series to provide the high total pressure.
Moreover, to avoid the interruption of operation due to the breakdown of the fans, a set of standby fan system is usually provided in series to the original fan system to avoid the system or device damage due to the interruption of the fan operation.
However, connecting two fans in series does not double the total pressure. Even if only one fan operates and the other stays still as a standby fan, the latter one reduces the total pressure of the fan in operation. The reason is that when the two fans are connected in series, the resistance between them increases and the operation efficiencies of them is decreased. Thus, in certain situations, for example in an air duct of an air conditioning system, the two axial-flow fans in series are separated far apart to minimize the interference between them. Nevertheless, this method is not feasible in the case that the installation space is limited.
Therefore, how to design an axial-flow serial fan with a plurality of rotor vanes that requires a small space and has the least interference effect becomes an important subject.
In view of the foregoing problems, an object of this invention is to provide an axial-flow serial fan with a plurality of rotor vanes, which reduces the air flow interference between the rotor vanes so that the total pressure of the serial fan with a plurality of rotor vanes can be increased.
Another object of the invention is to provide an axial-flow serial fan with a plurality of rotor vanes that occupies less space in its axial direction.
To achieve the above objects, an axial-flow serial fan comprises a single frame, a first rotor vane having at least one first blades; and a second rotor vane having at least one second blades, wherein the first rotor vane and the second rotor vane are provided in series in the single frame along an axial direction to minimize space occupied by the axial-flow serial fan in the axial direction.
According to the present invention, the design of each of the rotor vanes takes into account the air flow interference. The shape of the blade of each of the rotor vanes thus designed can improve the total pressure of the plurality of rotor vanes connected in series.
According to the present invention, since the plurality of rotor vanes are installed within a signal frame and the span between any two adjacent rotor vanes is minimized, therefore the volume of the fan in the axial direction can be greatly reduce.
Since the air flow is guided by directly using the relationship between the rotor vanes in accordance with the invention, there is no need to install extra elements for guiding air and the manufacturing cost and installation cost can be lowered.
Since there are a plurality of rotor vanes within a signal frame in accordance with the invention, some of the rotor vanes can be used as standby rotor vanes without affecting the total pressure of the active rotor vanes in operation.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.